The long-term goal of the proposed experiments is to understand how neurons containing peptides, an important class of neurotransmitter candidates, contribute to information processing in the retina of the macaque monkey. The experiments in the first 3-year period will focus on the 4 groups of peptides in the macaque retina: somatostatin, vasoactive intestinal peptide, neuropeptide Y, substance P, and the peptides structurally related to these. Extracts of macaque retina will be analyzed by high pressure liquid chromatography and radioimmunoassay. Light microscopic immunohistochemical studies will determine how many morphologically distinct types of neurons contain each of the peptides and their regional distribution. Subsequent experiments will combine immunohistochemical localization with another immunohistochemical or autoradiographic technique; the double-label experiments would indicate whether related peptides, unrelated peptides, or conventional neuro transmitters are found in the same cells as these peptides. Similar techniques modified for electron microscopy will identify the synaptic inputs and outputs of the peptidergic cells in the central retina. Computer-assisted 3-dimensional reconstruction from serial electron micrographs will be used to describe the labeled cells more completely and identify the unlabeled cells which are also contacted. These experiments combining biochemical and anatomical techniques would provide the basis for physiological studies of peptide release and actions in the primate retina. Of all the models used for vision research, the macaque monkey is the species in which both the structures of the peptides and synaptic connections of the neurons which contain them are most likely to be similar to the human. Recent studies indicate that peptidergic neurons are selectively affected by degenerative brain diseases. If this were also the case in some types of retinal diseases, this basic research on the function of primate retinal peptides would be valuable for understanding and, perhaps, treating these diseases.